Added Block Operations tutorial and code examples

doc/examples/Tutorial_BlockOperations_block_assignment.cpp

@@ -0,0 +1,31 @@
+#include <Eigen/Dense>
+#include <iostream>
+
+using namespace std;
+using namespace Eigen;
+
+int main()
+{
+  MatrixXf m(3,3), n(2,2);
+  
+  m << 1,2,3,
+       4,5,6,
+       7,8,9;
+       
+  // assignment through a block operation,
+  //  block as rvalue
+  n = m.block(0,0,2,2);
+  
+  //print n
+  cout << "n = " << endl << n << endl << endl;
+  
+  
+  n << 1,1,
+       1,1;
+        
+  // block as lvalue
+  m.block(0,0,2,2) = n;
+  
+  //print m
+  cout << "m = " << endl << m << endl;
+}